Manufacture of alumina and alkali compounds of sulfur.



5o lized a imrrnn s'rA'rns PATENT ort on ADoLF OLEMM, or MnNNHEIli, GERMANY." MANUFACTURE 'OF ALUMI'NA AIIND 'tLKAL l- COMPOUNDS Oi SIULFUR.

\ Specification of Letters Patent. Application filed Apr-i115, 1900. Serial 310,099; 1

Patented March 5, 1907.

If 0 all when!) it may cancer-m Be it known that I, ADOLF CLEMM, a sub- ,ject of the German Emperor, and a resident of Mannheim, Germany, have invented cer- 'ta'in new and useful Improvements in the Manufacture of Alumina and Alkali Compounds Containing Sulfur, of which the following is a specification.

This invention has for its object to convert ro bauxite or other aluminiferous material and alkalisulfate into alumina and sulfur-containing alkali compounds ,other than alkali sulfate. For this purpose alkali sulfate and carbon are intimately mixed with bauxite or 1 5 similar aluminiferous material whereby such proportions of the sulfate (and carbon) are used as are multiples of those theoretically required to form an alkali aluminate. As an bauxite (containing about sixty-one per cent. A1 0 are mixed with three hundred arts of sulfate of soda and sixty parts of car on, the

mixture being then calcined, the calcined mass lixiviated, andsulfurous-acid gas is introduced into the solution until the alumina is precipitated, thiosulfate remaining in solution. The reaction may be illustrated by the following equation:

but I do not confine myself to the proportions given, as the quality of the raw materials employed may render them more or less vari- 3 5 able. This mixture is calcined and the calcined mass "lixiviated with water, when an alkali aluminate and an excess of alkali sulfid are obtained in a solution which is generally of a yellowish or greenish color and can be clarified by allowing it to stand or by filtration. By treating this solution with sulfurous acid (preferably with the application of heat) the alumina of the bauxite used is obtained as a white precipitate of aluminium -4 hydroxid and the alkali sulfid contained in the solution is converted into alkali thiosulfate. The separated aluminium hydroxid is filtered off and washed and the solution may be evafiprated and treated to obtain crystalali thiosulfate.

Instead of treating the solution first with sulfurous acid it may be treated with sulfureted hydrogen, (preferably also with the application of heat.) In this case also the alumina is precipitated, and the remaining solution of alkali sulfohydrate and alkali sula form insoluble in water.

- fid is then treated with sulfurous acid in order to obtain the thiosulfate, However, the i said solution may also be used directlyfor instance, for reduction purposes in chemical manufactures-or sodium sulfid may be obtained from'it.

. The residue remaining after the lixiviation of the calcined massretains as a rule some alkali and sulfur com ounds,from which further quantities of t 'osulfate may be ob-' tained. This is effected by allowing the residue (t6 which some milkof lime-maybe added in order to accelerate the oxidation) to efiioresce in the air or by blowing air through the residue, the mass being thereupon lix1vi ated with water and thiosulfate allowed to crystallize'out of the liquor thus obtained after ithas beensuitably concentrated. example one hundred parts, by weight, of

It has often been attempted to replace the sodium carbonate by sodium sulfate and coal to produce the aluminate; but it was found that by using equivalent quantities of soand A1 0 the yield of alumina dissolved was less than in the sodium-carbonate process, while a considerable part of the sodium oxid was scorified-"that is, converted into It was further found that if an excess of sodium sulfate was used the lyes contained sulfid, which rendered them unsuitable for the recuperation of sodium in the form of-sodium carbonate. In the specification of the German Patent No. 62,265. it is stated that from theoretical considerations the use of a quantity of alkali greater than that which is the equivalent of the alumina is quite unnecessary and that the use of more alkali sulfate is even injurious, because it causes the lyes to be rich in sulfur. In the specification of the German 'dium'oxid and alumina (equal parts of Na,()

Patent No. 93,952 it is statedthat the invenaccessory formation of sulfids, so that it is evident from this that in decomposing the aluminate by carbon dioxid for the urpose of obtaining sodium carbonate all til tents of sulfid must be considered as a disadvantage. I have, however, found that the disadvantage referred to in the aforesaid s ecifications and the presence of sulfids in the solution of aluminate is advantageous if these solutions be converted into a sulfure'ted productsuch as alkali thiosulfate, alkali tor had succeeded in working without the.

e con- IIO the bauxite or the like and the rendering of the alumina soluble are all the more'perfect the more sodium sulfate and coal are used and that in using sodium sulfate two hundred per cent. in excess of the quantity equivalent to the alumina theo ening out of the bauxite or the like succee s as perfectly as with. sodium carbonate. I have further found that in using the aforesaid excess of sodium sulfate the losses in sulfur are much less than when only equivalent quantities of sodium oxid and alumina are taken, a portion of the sulfurbeing found in the yellowish to greenish lyes as polysulfid and that the much-feared compound of sodium sulfid and iron sulfid (see the specifications of German Patents No. 62,265 and 93,952) can be removed by oxidation in the air and utilized for obtaining thiosulfate, whereas they are injurious and the cause of losses when sodium carbonate is extracted.

The problem of how the solution of aluminate charged intentionally for a definite urpose with so large'an excess of alkali sul 'd is to be dealt with has been solved by me in the following manner: Instead of decomposing by carbon dioxid and obtaining sodium carbonate I use sulfurous acid or sulfureted hydrogen in order to obtain a sulfureted roduct, and I form in the first case thiosulate with the same quantity of sulfurous acid as is used to decompose the solution of aluminate and precipitate the alumina, whereas in the second case I likewise precipitate the alumina by means of sulfureted hydrogen and obtain sulfids and sulfohydrate. I have ,further found that the alkali salt, which (as in the sodium-carbonate process) becomes insoluble in water andis a source of loss, can be utilized in my process, as by oxidizing the residues remaining after the lixiviation a considerable portion of the alkali salt is obtained in a form soluble in waternamel y, in the form of thiosulfate.

The advantages of the process according to my invention may be summed up as follows: First, by using a very large excess of alkali sulfate andcoal the o ening out or rendering soluble of the bauxlte or the like is almost com lete; secondly, the rendering soluble of the auxite and the simultaneous formation of alkali sulfid are effected in one simple operation; thirdly, instead of precipitating by means of carbon dioxid and'obtaining alkali carbonate, alumina, and thiosulfate or sulfid and sulfohydrate in solution are obtained simultaneously or in one and,

the same operation by the use of sulfurous set forth.

2. The process of manufacturing alumina and alkali thiosulfate which consists of mixin aluminiferous material with quantities of al ali sulfate and carbon which are multiples of those. theoretically required to form an alkali aluminate and calcining the mixture, lixiviating the calcined mass and treatin the solution with sul'furo'us acid, substantial y as and for the purpose set forth.

3. The process of manufacturing alumina and thiosulfate, which consists in mixing aluminiferous material with uantities of alkali sulfate and carbo Whic are multiples of those theoretically re uired to form an alkali aluminate, calcining the mixture, lixiviating the calcined mass, treating the solution with sulfurous acid, treating the insoluble residues of lixiviation by oxidizing agents, treating the products of oxidation with water, concentrating the solution thus obtained and allowing the thiosulfate contained therein to crystallizeout as and for the purpose set forth. I

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

ADOLF CLEMM.

Witnesses:

H. W. HARRIS, Jos. H. LEUTE.

. acid or sulfuretedh drogen, and, fourthl ,the 

